A polarizer is a device that transforms unpolarized or mixed polarization electromagnetic waves into polarized waves. Polarizers have found a wide array of practical applications such as in photographic filters, microscopes, optoelectronics, lasers, and liquid crystal displays. Wave plates or retarders are optical devices that can change the polarization of electromagnetic waves. Wave plates are often used to control the polarization of waves and therefore are involved in many of the same applications as polarizers. Many prior art devices rotate polarizers or wave plates relative to one another to vary the angle between polarization or optic axes. For example, polarization filters for photography may involve rotating a polarizer to vary the intensity of light transmission through the filter.
When two linear polarizers are disposed facing one another, the second polarizer is generally called an analyzer. When the polarization axis of the polarizer and analyzer are parallel, the amount of light transmittance is maximized. If the two axes are orthogonal the polarizers are crossed, in theory, no light is transmitted. Furthermore, rotation of one polarizer with respect to the other will result in partial light blockage over the range of transmittances between a minimum and maximum transmittance.
Thus, the rotation of one polarizer with respect to another or rotation of a wave plate placed between two crossed polarizers will result in a variation of light transmittance. Unfortunately, most applications for controlled partial light transmittance do not conveniently allow for rotation of an optical element. Thus, there is a widely recognized need for a device that uses polarizers to control light transmittance amounts and that does not require rotation of a polarizer.